Battery packs have been used in automotive and industrial applications for many years. Traditionally, these battery packs use a relatively small number of large battery cells, typically lead-acid type battery cells. A battery pack design that uses a small number of large battery cells has several disadvantages. First, if one of the cells fails, a substantial percentage of the overall energy capacity would be lost. For example, for a pack using 11 cells, a single cell failure would result in a 9% loss of total capacity. Second, such a battery pack has poor thermal cooling efficiency. The cooling efficiency of a cell is proportional to the cell's surface-area-to-volume ratio. A larger cell has a smaller surface-area-to-volume ratio compared to that of a smaller cell. Battery cells degrade when subject to elevated temperatures. For example, lithium-ion batteries lose 20% of their usable charge within three months when subjected to 60° C. temperature; in contrast, they will lose the same percentage of charge in three years when the temperature is held at 25° C. Therefore, heat dissipation is an important factor in the design of a battery pack.
Recently, high-density, small form-factor battery cells, previously limited to relatively low-power (and therefore low cell-count) applications such as laptop computers and power tools, have been proposed for high cell-count automotive and industrial battery packs. Unfortunately, such battery packs tend to be tremendously expensive, due in part to the large number of pack components and the complexity involved in interconnecting such a large number of cells 210 using conventional interconnection techniques (e.g., conducting wires 104 coupled from respective cell terminals 106 to a metal plate 102 as shown in FIG. 1A, or a metal strip 110 welded to cell terminals 106 as shown in FIG. 1B). Moreover, conventional cell interconnections (welded wires or strips) are susceptible to failure when the cells dislocate slightly during operation, for example, due to vibration within a moving vehicle.